It's not that binary. Usually, you have to know what a word refers to, not what it means.I am not one to explore the meaning of words too deeply but if you are claiming that using the words "tsume" is significant I either have to know what it means or simply not know what you are talking about.
If I ask you what colour livid is, the odds are at least 6-to-1 that we will differ. But if I say "I was livid", you will assume instantly that I was angry. That is because with the simple word "I" I have defined the context. In the same way, a go commentator defines a context. You should then tune into his wavelength.
We communicate by using probabilities, not definitions. Very few people can define "plastic" (in any of its senses) but we use probabilities to distinguish the various senses in a "plastic toy" and a "plastic face." We may even bring in associations: a favourite toy from childhood, or memories of mime artist Marcel Marceau. Communication is very definitely a bipolar process where we bring extra information to the discourse without sometimes even expressing all the elements present. If someone says to us, that's a "plastic material" our probability function can go haywire: made of a polymer material or something that's bendy - or breakable? We need more context. In normal discourse, we wouldn't then say: define plastic. We would just say (as you did), what do you mean? But as soon our interlocutor tells us, perhaps obliquely ("I mean it's a fire hazard") our brain latches instantly on to what is being referred to. And other parts of our brains also light up: where are the fire exits, have we got a fire extinguisher, or calm down and don't overreact.
Go commentaries work in just the same way. When Shusai says, "The tsume may be better" and plonks a stone on the board, we have a point of reference and our brain (subconsciously) takes note of all the associations elsewhere on the board, or remembering a previous game - or a discussion on L19 (if that's not too much of an oxymoron). Eventually, when we hear this word often enough, we will start to feel we know what it means without having any definitions, just as we think we know what plastic means without knowing what a polymer is. We will even, without conscious effort learn that Shusai's tsume has nothing to with tsume go.
Why can't L19 or SL operate with the same normal standard of communication? Is it something to do with how younger players have been learning about the game? They watch videos instead of reading books? They just play instead of studying? They get transfixed before the AI cobra instead of talking to humans? Are they trolling? I dunno.